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Peter Anvin" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andy Lutomirski , Dave Hansen , Josh Poimboeuf , Juergen Gross , Peter Zijlstra , Borislav Petkov , Jiri Kosina , Boris Ostrovsky , Brian Gerst , David Laight , Denys Vlasenko , Eduardo Valentin , Greg KH , Will Deacon , aliguori@amazon.com, daniel.gruss@iaik.tugraz.at, hughd@google.com, keescook@google.com, Andrea Arcangeli , Waiman Long , Pavel Machek , "David H . Gutteridge" , jroedel@suse.de, joro@8bytes.org Subject: [PATCH 36/37] x86/mm/pti: Add Warning when booting on a PCID capable CPU Date: Mon, 23 Apr 2018 17:47:39 +0200 Message-Id: <1524498460-25530-37-git-send-email-joro@8bytes.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1524498460-25530-1-git-send-email-joro@8bytes.org> References: <1524498460-25530-1-git-send-email-joro@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joerg Roedel Warn the user in case the performance can be significantly improved by switching to a 64-bit kernel. Suggested-by: Andy Lutomirski Signed-off-by: Joerg Roedel --- arch/x86/mm/pti.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index e3059bb0..0ab41fb 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -497,6 +497,22 @@ void __init pti_init(void) pr_info("enabled\n"); +#ifdef CONFIG_X86_32 + if (boot_cpu_has(X86_FEATURE_PCID)) { + /* Use printk to work around pr_fmt() */ + printk(KERN_WARNING "\n"); + printk(KERN_WARNING "************************************************************\n"); + printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! **\n"); + printk(KERN_WARNING "** **\n"); + printk(KERN_WARNING "** You are using 32-bit PTI on a 64-bit PCID-capable CPU. **\n"); + printk(KERN_WARNING "** Your performance will increase dramatically if you **\n"); + printk(KERN_WARNING "** switch to a 64-bit kernel! **\n"); + printk(KERN_WARNING "** **\n"); + printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! **\n"); + printk(KERN_WARNING "************************************************************\n"); + } +#endif + pti_clone_user_shared(); /* Undo all global bits from the init pagetables in head_64.S: */ -- 2.7.4